This invention relates generally to water and wastewater treatment and more particularly with clarifiers used for clarifying water and wastewater through flocculation and settlement of solids. Still more particularly, the invention is directed to a method and apparatus for dissipating the energy of the influent that is directed into the feedwell of a clarifier in order to enhance flocculation of the influent.
In the treatment of water and wastewater, clarifiers are commonly used for settling of floc in order to clarify the liquid. The influent is typically introduced into the clarifier through an influent feed structure that may take the form of a central influent column, a feed pipe, or a feed trough. A feedwell that takes the form of a cylindrical ring generally centered in the clarifier initially receives the influent. In order to enhance flocculation of the influent and promote settling of the floc, it is helpful to minimize the energy of the influent that enters the feedwell.
Various types of energy dissipating feedwells and devices for dissipating the energy of the influent entering the feedwell have been proposed. For example, U.S. Pat. No. 6,276,537 to Esler discloses a feedwell which is closed at the bottom and equipped with pipes that extend from the bottom of the feedwell and direct the flow that discharges from the feedwell in opposite directions. In a configuration of this type, the dissipation of energy takes place well below the feedwell and outside of its confines rather than within the feedwell. Thus, the flocculation time is reduced compared to a situation where the energy dissipation occurs within the feedwell, and the flocculation suffers accordingly.
Other configurations promote swirling of the influent within the feedwell, as exemplified by U.S. Pat. No. 3,926,805 to Walker, U.S. Pat. No. 3,216,570 to Cunetta and U.S. Pat. No. 3,006,474 to Fitch. Influent that moves in a swirling pattern has significant energy that can result in a short circuit flow and improper flocculation. Other efforts to dissipate energy are disclosed in U.S. Pat. No. 3,175,692 to Vrablik and U.S. Pat. No. 2,702,124 to Stengel, neither of which has been commercially successful. Adjustable feedwell ports such as those shown in U.S. Pat. No. 4,270,676 to Green have been proposed but have not been particularly effective in promoting flocculation.
The present invention is directed to an inlet structure that is installed within a feedwell and constructed to dissipate the energy of the influent in order to inhibit short circuiting of the clarification process and enhance flocculation, along with a method employed in the dissipation of energy.
It is an object of the invention to provide, in a clarifier feedwell, an energy dissipating inlet which is improved in its ability to dissipate energy and enhance flocculation.
Another object of the invention is to provide a method of dissipating influent energy by directing streams of influent tangentially in opposite directions into impingement with other streams in a manner to dissipate energy due to interaction between the impinging and oppositely directed influent streams.
A further object of the invention is to provide an energy dissipating inlet of the character described in which the degree of impingement and influent velocity at the time of impingement can be controlled through simple adjustments.
An additional object of the invention is to provide an energy dissipating inlet of the character described that is simple and economical to construct and install and useful with a wide variety of feedwells and clarifier configurations.
In accordance with a preferred embodiment of the invention, an inlet structure for a feedwell includes a cylindrical wall and a closed bottom. The inlet structure is installed within and generally centered in the feedwell in order to receive the influent discharged into the clarifier basin from the influent feed structure. The wall of the inlet structure is provided with ports that are spaced apart circumferentially and equipped with baffles arranged to direct the influent tangentially in opposite directions. The influent streams impinge with oppositely directed streams from the adjacent ports in order to dissipate their energy as the influent enters the feedwell. Accordingly, the energy is dissipated within the feedwell, and adequate time for effective flocculation is provided.
Preferably, each baffle is constructed with a fixed center vane located immediately in front of the port, two hinged gates on the opposite sides of the center vane, and a bottom baffle extending beneath the port and underlying the center vane and both gates. The gates can be swung inwardly to direct the streams of influent closer to the inlet wall and increase the velocity due to the decrease in area. Conversely, the gates can be adjusted outwardly to decrease the velocity and create a larger area of impingement between the influent streams.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.